How to store the output of a loop in a matrix/vector when the loop is not indexed?

Question

Laura Ramirez 2014-5-29

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/131602-how-to-store-the-output-of-a-loop-in-a-matrix-vector-when-the-loop-is-not-indexed

编辑： Andrei Bobrov 2014-5-29

Hi everyone, I'm new in matlab and i need to store the output of a loop in a vector. the problem is that the loop is not indexed therefore i cannot create a vector of zeros where to store the output. My code looks as follows

 a=-1;
 b=-1;
 p=-0.5;
 a1 = a./sqrt(2*(1-p^2));
 b1 = b./sqrt(2*(1-p^2));
 for xj = [0.10024215,0.48281397,1.0609498,1.7797294,2.6697604];
       xi = [0.10024215,0.48281397,1.0609498,1.7797294,2.6697604]'; 
       f1 = sum(exp( a1.*(2*xi - a1) + b1.*(2*xj-b1) + 2*p.*(xi-a1).*(xj-b1)))
 end

and my output looks as follows

 f1 =
   0.121232883313475
 f1 =
   0.043069611850309
 f1 =
   0.009189704089853
 f1 =
   0.001377436854364
 f1 =
     1.344664406705558e-

I need to store that in a vector. Could somebody please tell me what's the correct way to do it ? Thaanks :)

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Answer 1

Andrei Bobrov 2014-5-29

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/131602-how-to-store-the-output-of-a-loop-in-a-matrix-vector-when-the-loop-is-not-indexed#answer_138711

编辑：Andrei Bobrov 2014-5-29

在 MATLAB Online 中打开

a=-1;
b=-1;
p=-0.5;
a1 = a./sqrt(2*(1-p^2));
b1 = b./sqrt(2*(1-p^2));
x = [0.10024215,0.48281397,1.0609498,1.7797294,2.6697604];
[xi,xj] = ndgrid(x);
f1 = sum(exp( a1.*(2*xi - a1) + b1.*(2*xj-b1) + 2*p.*(xi-a1).*(xj-b1)));

with use bsxfun

f1 = sum(exp(...
     bsxfun(@plus,a1*(2*x(:)-a1),b1*(2*x(:)'-b1)) + 2*p*(x(:)-a1)*(x(:)'-b1)),2);

or with loop for..end

n = numel(x);
f1 = zeros(n,1);
f = zeros(n);
for jj = 1:n
    for ii = 1:n
        f(ii,jj) = exp(a1.*(2*x(ii) - a1)...
                               + b1.*(2*x(jj)-b1) + 2*p.*(x(ii)-a1).*(x(jj)-b1));
    end
    f1(jj) = sum(f(:,jj));
end